1. Field of the Invention
The present invention relates to a method of delivering multicast packets in a mesh network, and more particularly, to a method of delivering multicast packets and preventing multi-paths in a mesh network.
2. Description of the Prior Art
Wireless mesh network (WMN) is a key technology for next-generation wireless networks. The wireless mesh network supports ad-hoc networking and has the self-organization and self-configuration properties. The wireless mesh network serves as an access network that employs multi-hop wireless forwarding by non-mobile nodes to relay data to and from Internet. It was announced that the wireless mesh network could provide data transmission rate up to 134.4 mbps, which satisfies the requirement of the next-generation high-speed wireless networks.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a wireless mesh network according to the prior art. The wireless mesh network comprises two kinds of mesh nodes, a mesh portal (MB) 12 and mesh access points (MP) 14. The mesh portal 12 is a gateway between the Internet and the wireless mesh network, for delivering data from the wireless mesh network to the Internet, or from the Internet to the wireless mesh network. The mesh access point 14 provides a wireless network service directly to a mobile station (MS) 16 through a wireless access link. When the radio of the mesh access points 14 can cover each other, a wireless mesh link exists between the two mesh access points 14 and each of two mesh access points 14 can deliver the data through the link. The mesh access points 14 and the mesh portal 12 construct a mesh distribution system. In other words, the mesh access points 14 communicates with the mesh portal 12 through a mesh network protocol, and the mesh access point 14 communicates with the mobile station 16 through many protocols, such as IEEE 802.11 and mobile telecommunication network.
When the mobile station 16 enters the service range of the mesh access point 14, the mobile station 16 performs an association procedure to establish a wireless mesh link with the mesh access point 14. The mesh access point 14 is a serving mesh access point of the mobile station 16. Through the wireless mesh network, the mobile station 16 can communicate with other mobile stations 16 in the wireless mesh network or other hosts in the Internet. For example, the data delivering to the mobile station 16 are relayed between different mesh access points 14, and the data are delivered to the serving mesh access point of the mobile station 16 finally. In the wireless mesh network, each mesh access point 14 delivers not only the data of the mobile station 16 in the service range but also the data from other mesh access point 14. In addition, the wireless communication uses the broadcast transmission. If the transmission between each mesh access point 14 is not scheduled effectively, the transmission of the mesh access point 14 may collide so as to reduce the performance of the wireless mesh network. Thus, there is a protocol to control the period or frequency of the transmission of each mesh access point 14, which is the medium access control (MAC) protocol of the wireless network. In addition, before delivering the data to the mobile station 16, the mesh access point 14 has to determine which mesh access point 14 is the serving mesh access point of the mobile station 16. The mobile station 16 can move so it may associate with different serving mesh access point. Thus, a mobility management and a routing mechanism are specified in the network layer of the protocol of the wireless network.
Please refer to FIG. 2 and FIG. 3. FIG. 2 to FIG. 3 are schematic diagrams of mesh access points delivering a multicast packet according to the prior art. The wireless mesh network comprises four mesh access points, and between each mesh access point has a wireless mesh link. A first mesh access point 121 (source terminal) uses a multicast transmission to break a frame into multiple unicast packets and deliver the packets to each peer mesh access point respectively. On receipt of the packet, the mesh access point forwards the packet to each peer mesh access point using same mechanism. The same packet will be delivered many times since multi-paths exist in the mesh network. As shown in FIG. 2, the first mesh access point 121 delivers a multicast packet to the second, third, and fourth mesh access point 122, 123, 124. As shown in FIG. 3, the second, third, and fourth mesh access point 122, 123, 124 forward the multicast packet to the peer mesh access point. Accordingly, the forwarding multicast packets are unnecessary and waste the channel resource.